This invention relates to a ventilating apparatus and more particularly, to a ventilating suction and exhaust fan device of Sirocco type in which when exhaustion and suction of enormous volumes of air are simultaneously carried out by means of a centrifugal fan, the flows of suction air and of exhaust air are both converted from centrifugal flows to axial flows and the possibility of mixing of the exhaust air and the suction air is completely eliminated.
Recently, many types of ventilators have come into use for ventilating rooms. However, these ventilators, which consist only of axial fans, are not satisfactory. Further, with these ventilators, air is sucked by reversing the direction of rotation of the fans, and this decreases the efficiency of the ventilators. Further, if only one such ventilator is used for ventilating a closed room in which offensive smell is continuously generated, the generated offensive smell is exhausted out of the room in the beginning; but, as time goes on, the air pressure in the room gradually decreases and, accordingly, the ventilator's efficiency of exhausting the offensive smell is also gradually reduced and at last the room is filled with the offensive smell and persons in the room have difficulty in breathing. Axial fans in which suction and exhaustion of air are simultaneously carried out are known. However, such fans have not been practically employed, since their efficiency is relatively low and they mix exhaust air with suction air.
In these circumstances, after many experiments and long investigation, the Applicant proposed a ventilating suction and exhaust fan device in which suction of air and exhaustion of air are simultaneously carried out by a fan of Plate type, thereby eliminating some of the disadvantages described above. However, this Plate type fan device has inherent disadvantages. One is that the size of the fan device is large relative to the volume of air to be handled by said fan device. Another is that the ventilating efficiency of said fan is relatively low, since a relatively large volume of exhaust air is mixed with suction air due to the fact that clearances between the circumference of the impeller and edges of the rectangular opening of the partition plate within which the impeller is mounted can not be completely sealed.
Subsequently, the Applicant proposed a fan device of Sirocco type comprising a rectangular casing, a cylindrical impeller rotatably mounted within the casing with its axis positioned perpendicular to the central axis of the casing, and two partition plates extending in a common horizontal plane passing through the central axis of the casing, the inner terminal edges of the plates being closely adjacent to the circumference of the impeller. The fan device of this construction is relatively compact, can be easily manufactured and can handle a relatively large volume of air, and the working efficiency of the fan device is improved by reducing mixing of the exhaust air and the suction air. However, in this known Sirocco type fan device, mixing of the exhaust air and the suction air is not completely eliminated, and therefore, the efficiency of the fan device is not satisfactory.